1. Field of the Invention
The invention relates to the field of photography, and particularly to a photosensitive material processing apparatus.
2. Description of the Prior Art
The processing of photographic film involves a series of steps such as developing, bleaching, fixing, washing, and drying. These steps lend themselves to mechanization by conveying a continuous web of film or cut sheets of film or photographic paper sequentially through a series of stations or tanks, each one containing a different processing liquid appropriate to the process step at that station.
There are various sizes of photographic film processing apparatus, i.e., large photofinishing apparatus and microlabs. A large photofinishing apparatus utilizes tanks that contain approximately 100 litres of each processing solution. A small photofinishing apparatus or microlab utilizes tanks that may contain less than 10 litres of processing solution.
The chemicals contained in the photographic solution: cost money to purchase; change in activity and leach out or season during the photographic process; and after the chemicals are used the chemicals must be disposed of in an environmentally safe manner. Thus, it is important in all sizes of photofinishing apparatus to reduce the volume of processing solution. The prior art suggests various types of replenishing systems that add or subtract specific chemicals to the photographic solution to maintain a consistency of photographic characteristics in the material developed. It is possible to maintain reasonable consistency of photographic characteristics only for a certain period of replenishment. After a photographic solution has been used a given number of times, the solution is discarded and a new photographic solution is added to the tank.
Activity degradation due to instability of the chemistry, or chemical contamination, after the components of the photographic solution are mixed together causes one to discard the photographic solution in smaller volume tanks more frequently than larger volume tanks. Some of the steps in the photographic process utilize photographic solutions that contain chemicals that are unstable, i.e., they have a short process life. Thus, photographic solutions in tanks that contain unstable chemicals are discarded more frequently than photographic solutions in tanks that contain stable chemicals.
The prior art realized that if the volume of the various tanks contained within various sizes of photographic processing apparatus were reduced the same amount of film or photographic paper may be processed, while reducing the volume of photographic solution that was used and subsequently discarded. One of the problems encountered by the prior art in using smaller volume tanks was that the space was limited so that there was not sufficient space available to allow the drives utilized in the prior art to move the film and/or paper.
One of the techniques utilized by the small volume processing tank prior art to reduce the volume of processing solution was to place the drive mechanisms including idlers, tensioners, and other drive components on the outside of the tank. A disadvantage of the above technique was that the drive mechanism had to pass through the walls of the tank, breaking the fluid retaining integrity of the tank. Thus, the drive mechanism required seals to prevent processing solution from leaking out of the tanks. The seals increased the cost of the drive mechanism, required additional maintenance and reduced the reliability of the drive mechanisms.
Another technique utilized by the small volume processing tank prior art was to place the drive mechanisms on the inside of the processing tank. The major disadvantage of the above technique was that the volume of processing solution was increased in order to fill the voids created by placing the drive mechanism on the inside of the tank.